The objective of the proposed research is to study the mechanisms associated with transduction in hair cell organs of the lateral line and vestibular systems. We propose to investigate the dynamic relationships between water flow, cupula motion, receptor potentials, membrane conductance changes, synaptic processes, and afferent nerve responses. We also propose to directly test in lateral line organs the postulated relationship between morphological orientation and directional sensitivity of hair cells. Established electrode techniques will be employed in recording from and staining hair cells intracellularly and in recording nerve impulse activity. Conductance changes will be determined by standard bridge circuitry or voltage clamp methods. Synaptic activation in the absence of mechanical stimulation will be produced by galvanic current. We propose to control stimuli, analyze receptor potentials, and reduce nerve spike data by means of a small on-line computer facility. We propose to study the relationship of cupular motion to nerve responses in the semicircular canals, particularly with respect to origins of neural adaptation. Concentrations of ions in endolymph and perilymph will be determined and their roles in hair cell transduction and synaptic function explored by observing the effects on spontaneous and evoked activity of varying the concentratons in the extracellular fluids. BIBLIOGRAPHIC REFERENCES: L.S. Frishkopf, C.M. Oman, and K. Baden-Kristensen, "Studies of Receptor Potentials in Lateral Line Hair Cells," RLE Progress Report No. 115, Research Laboratory of Electronics, M.I.T., Cambridge, Mass., January 1975, p. 309. C.M. Oman and L.S. Frishkopf, "Studies of Transduction in the Semicircular Canals of Fish," RLE Progress Report No. 115, Research Laboratory of Electronics, M.I.T., Cambridge, Mass., January 1975, pp. 309-310.